命令模式

類圖：

常用的實現方式：

指令處理對象

public interface IReceiver  {

        void Operation();
    }//end IReceiver

public class ReceiverA : IReceiver {

        public ReceiverA(){

        }

        public void Operation(){
            Console.WriteLine("由ReceiverA處理");
        }

    }//end ReceiverA
 

public class ReceiverB : IReceiver {

        public ReceiverB(){

        }

        public void Operation(){
            Console.WriteLine("由ReceiverB處理");
        }

    }//end ReceiverB

指令對象

public interface ICommand  {

        void Execute();
    }//end ICommand

public class CommandRealizeA : ICommand {

        private readonly IReceiver _receiver;

        public CommandRealizeA(){
            _receiver=new ReceiverA();
        }

        public void Execute(){
            _receiver.Operation();
        }

    }//end CommandRealizeA

public class
 
 CommandRealizeB : ICommand {

        private readonly IReceiver _receiver;

        public CommandRealizeB()
        {
            _receiver=new ReceiverB();
        }

        public void Execute(){
            _receiver.Operation();
        }

    }//end CommandRealizeB

調用對象

public class Invoker {

        private ICommand _command;

        public Invoker(){
            _command=new CommandRealizeA();//默認指令
        }

        public void Invoke()
        {
            _command.Execute();
        }

        /// 
        /// <param name="command"></param>
        public void SetCommand(ICommand command)
        {
            _command = command;
        }

    }//end Invoker

使用場景：

當每次請求或者動作會出現一連串操作,此時可以考慮。比如提交表單後臺涉及到數據庫操作，日誌操作，緩存操作等等，這些操作可以用命令模式去控制。

命令模式將命令的調用者（發出者），執行者，處理著，從一個緊耦合的動作，分離開來，主要用來復雜的動作解耦和指令（命令）管理。

設計模式面對面之命令模式